Conventionally, Kovar (Fe-29Ni-16Co), 42 Alloy (Fe-42% Ni), stainless steel disclosed in JP-A-63-293143 and so on have been used as a material of electronic and magnetic parts in semiconductor equipment or the like. However, those alloys have a problem that they are expensive, and they also have a problem that they are inferior in conductivity and heat-radiation efficiency. In order to improve these characteristics, therefore, a copper (Cu) base alloy has come into use recently.
The Cu-base alloy of which copper content is 90% or more is low in the strength. Consequently, it is effective to add iron to the Cu-base alloy as a strengthening element, and to add chromium to it, as disclosed in JP-A-49-91025 (an alloy for sliding contact parts of electric equipments) or the like, so as to improve the corrosion resistance property as well. Moreover, as disclosed in Iron and Steel Handbook, the third edition, Vol. IV, pp. 211-212 (compiled by Japan Iron and Steel Association), adding molybdenum to improve the corrosion resistance property is a known method. The problem is, however, that additions of such alloying elements deteriorate uniformity of the alloy.
It should be noted that the Fe--Cu--Cr alloy which is disclosed in JP-A-49-91025 is not intended as a material of electronic and magnetic parts. Although the stainless steel for an electronic material which is disclosed in JP-A-63-293143 is intended for the same kind of use, it has obviously different elements in the compositions. Further, an alloy strip manufacturing method disclosed in JP-A-60-152640 is obscure in the kind of composition, restriction of additive elements, and effective concentration ratios. Furthermore, none of these preceding techniques discloses any suggestion concerning the manufacture of an Fe--Cu alloy having high uniformity which is the object of the present invention, so that it is doubtful whether such an alloy can be manufactured or not.
Among Fe--Cu alloys, for example, an alloy containing 50% copper exhibits a uniform liquid phase unless it contains chromium. However, if it contains 3% or more chromium, when it is melted, it becomes a molten liquid which is divided into a liquid phase rich in iron and another liquid phase rich in copper. If such an alloy having two divided phases, i.e., the liquid phases rich in iron and copper respectively, is cast, a uniform product can not be obtained. That is to say, grains in the iron-rich liquid phase and grains in the copper-rich liquid phase increase in size during the melting operation, and after they solidify, there are generated crackings in interfaces between those two phases during cold working, causing disadvantages such as poor bending characteristics of final products.